Staying slightly off topic - as is my wont - do you think our perception of too skinny, too fat etc depends on our own body type (or body image)?
I'm a lot skinnier than I was a couple of years ago, and I find I look at people I know and think "God, they're fat"... but they haven't changed, I have! It's not a conscious thing, my mental image of myself hasn't really changed but I obviously have changed my perception/basis of comparison without really realising it.